Ion sources are widely used to generate ion beams in materials processing applications. Such ion sources often include grid optics to produce an ion beam with a relatively narrow range of ion energy. The ion sources also often have features to help control spatial and charged state attributes of the ion beam such as beam current density or flux, uniformity or spread, divergence or focus, and neutralization.
The ion beams serve a wide variety of materials processing applications including ion beam sputtering, ion milling, surface etching, ion assist during deposition, surface texturing, and pre-cleaning in order to pattern, produce, or “grow” various surface structures or alter surface properties on a substrate. Such ion beams are also used in a host of direct or indirect thin film deposition processes including ion beam physical vapor sputter deposition and direct film deposition (e.g., silicon carbon based or diamond like carbon coatings). The ion beams may also be used as an energetic ion assist to magnetron, e-beam evaporator, or secondary ion beam deposition processes for the formation of either conductive or dielectric films. Example ion beam source applications include ion beam milling and/or etching of surface layers to from sub-micron features within data-storage read/write heads. Another example is using one or more ion sources for deposition and densification of oxides, nitrides or fluoride-based thin films onto an optical substrate while impinging the same substrate with a secondary “assist” ion beam in order to produce films with high optical index and clarity and with controlled material properties such as adhesion, stress, or density. Yet another example of using an ion beam for materials processing includes surface treatment of moving architectural glass substrates undergoing vacuum based processing, or metal or polymer films in a vacuum web coating system. In such example implementations, ion beam(s) can be used for surface cleaning, texturing, deposition assist, surface chemistry activation, and/or the formation or growth of nanometer-scaled surface structures.
The ion beam sources often incorporate a low pressure, electrically excited gas discharge (or gaseous plasma) that is driven by the inputs of multiple electrical power supplies having a variety of power handling characteristics. Each ion beam source may further include one or more grids that electrically extract and form the ion beam. In another implementation, each ion beam source may include magnetic fields in close proximity to a positive anode body to support a plasma space-charge that is used to form an ion beam. Typically, one or more power supplies, which form an ion source power supply system, initiate and sustain an electrically excited gas discharge body to form the ions, extract and accelerate the ions to form an ion beam, and further assist in neutralization of the electrical space charge of the ion beam.
Ion source power supply systems may include one or more sub-systems that are electrically coupled with each other through some form of plasma or gas-discharge impedance. These sub-systems are susceptible to shorting events or open faults between components of the power supply system, which can lead to damage of one or more power supplies involved in the fault and/or will shut down of the ion source power supply system. Further, the power supplies may also be susceptible to input line “fault” conditions such as loss of a voltage alternating current (VAC) phase (from a three phase input) or a line sag, when the voltage to one or more of the input VAC line phases drops below a minimum value. In one implementation, this low input VAC condition causes a diminished power handling capacity of a VAC-DC converter supporting a DC bus, which delivers power to various ion source power supply modules. Existing approaches for protecting multiple and different power supplies against the numerous varieties of potential fault conditions involve sizeable power absorbing protection circuitry at the outputs of each power supply, which introduces excess cost to the ion source power supply systems. Moreover, such existing approaches do not intelligently mitigate persistent or transient fault conditions and do not automatically recover from a fault event/condition and return the ion source power supply system (and thereby the ion source) to a desired state of operation.